scholarly journals Selection responses of means and inbreeding depression for female fecundity in Drosophila melanogaster suggest contributions from intermediate-frequency alleles to quantitative trait variation

2007 ◽  
Vol 89 (2) ◽  
pp. 85-91 ◽  
Author(s):  
BRIAN CHARLESWORTH ◽  
TAKAHIRO MIYO ◽  
HELEN BORTHWICK
Keyword(s):  
Drosophila Melanogaster ◽  
Inbreeding Depression ◽  
Quantitative Trait ◽  
Balancing Selection ◽  
Evolutionary Genetics ◽  
Intermediate Frequency ◽  
Female Fecundity ◽  
Deleterious Alleles ◽  
The Mean ◽  
Change In Mean

SummaryThe extent to which quantitative trait variability is caused by rare alleles maintained by mutation, versus intermediate-frequency alleles maintained by balancing selection, is an unsolved problem of evolutionary genetics. We describe the results of an experiment to examine the effects of selection on the mean and extent of inbreeding depression for early female fecundity in Drosophila melanogaster. Theory predicts that rare, partially recessive deleterious alleles should cause a much larger change in the effect of inbreeding than in the mean of the outbred population, with the change in inbreeding effect having an opposite sign to the change in mean. The present experiment fails to support this prediction, suggesting that intermediate-frequency alleles contribute substantially to genetic variation in early fecundity.

scholarly journals Selection, Load and Inbreeding Depression in a Large Metapopulation

Genetics ◽  
2002 ◽  
Vol 160 (3) ◽  
pp. 1191-1202 ◽  
Author(s):  
Michael C Whitlock
Keyword(s):  
Population Structure ◽  
Inbreeding Depression ◽  
Population Subdivision ◽  
Response To Selection ◽  
Mutation Load ◽  
Deleterious Alleles ◽  
Subdivided Population ◽  
Soft Selection ◽  
Mean Fitness ◽  
The Mean

Abstract The subdivision of a species into local populations causes its response to selection to change, even if selection is uniform across space. Population structure increases the frequency of homozygotes and therefore makes selection on homozygous effects more effective. However, population subdivision can increase the probability of competition among relatives, which may reduce the efficacy of selection. As a result, the response to selection can be either increased or decreased in a subdivided population relative to an undivided one, depending on the dominance coefficient FST and whether selection is hard or soft. Realistic levels of population structure tend to reduce the mean frequency of deleterious alleles. The mutation load tends to be decreased in a subdivided population for recessive alleles, as does the expected inbreeding depression. The magnitude of the effects of population subdivision tends to be greatest in species with hard selection rather than soft selection. Population structure can play an important role in determining the mean fitness of populations at equilibrium between mutation and selection.

scholarly journals The rate of selection advance for non-additive loci

1969 ◽  
Vol 13 (2) ◽  
pp. 165-173 ◽  
Author(s):  
W. G. Hill
Keyword(s):  
Inbreeding Depression ◽  
Quantitative Trait ◽  
Half Life ◽  
Gene Frequency ◽  
Gene Action ◽  
Dominant Gene ◽  
Single Locus ◽  
Dominant Allele ◽  
Total Change ◽  
The Mean

Expected changes in the gene frequency and the population mean for a quantitative trait are described for selection in a population of size N at a single locus where the favoured allele has initial frequency q0 and selective value s. Models of additive and completely dominant gene action are compared. Results are generally expressed as the half-life of the total change relative to N.If the favoured allele is additive or recessive the half-life of the gene frequency and mean of the trait are usually reduced when q0 or Ns is increased. However, if the dominant allele is favoured the half-life of gene frequency is still generally reduced as Ns is increased, but has a minimum at low or intermediate values of q0. Since inbreeding depression and selection oppose each other when the dominant allele is favoured the response in the mean of the quantitative trait may change in direction during selection.

scholarly journals Neutral mutation as the source of genetic variation in life history traits

2005 ◽  
Vol 86 (1) ◽  
pp. 53-63 ◽  
Author(s):  
KRUNOSLAV BRČIĆ-KOSTIĆ
Keyword(s):  
Genetic Variation ◽  
Life History ◽  
Quantitative Trait Loci ◽  
Quantitative Trait ◽  
Life History Traits ◽  
Balancing Selection ◽  
Evolutionary Genetics ◽  
Relative Fitness ◽  
Adaptive Genetic Variation ◽  
Trait Loci

The mechanism underlying the maintenance of adaptive genetic variation is a long-standing question in evolutionary genetics. There are two concepts (mutation–selection balance and balancing selection) which are based on the phenotypic differences between alleles. Mutation – selection balance and balancing selection cannot properly explain the process of gene substitution, i.e. the molecular evolution of quantitative trait loci affecting fitness. I assume that such loci have non-essential functions (small effects on fitness), and that they have the potential to evolve into new functions and acquire new adaptations. Here I show that a high amount of neutral polymorphism at these loci can exist in real populations. Consistent with this, I propose a hypothesis for the maintenance of genetic variation in life history traits which can be efficient for the fixation of alleles with very small selective advantage. The hypothesis is based on neutral polymorphism at quantitative trait loci and both neutral and adaptive gene substitutions. The model of neutral – adaptive conversion (NAC) assumes that neutral alleles are not neutral indefinitely, and that in specific and very rare situations phenotypic (relative fitness) differences between them can appear. In this paper I focus on NAC due to phenotypic plasticity of neutral alleles. The important evolutionary consequence of NAC could be the increased adaptive potential of a population. Loci responsible for adaptation should be fast evolving genes with minimally discernible phenotypic effects, and the recent discovery of genes with such characteristics implicates them as suitable candidates for loci involved in adaptation.

scholarly journals MAINTENANCE OF GENETIC VARIABILITY UNDER THE PRESSURE OF NEUTRAL AND DELETERIOUS MUTATIONS IN A FINITE POPULATION

Genetics ◽  
1979 ◽  
Vol 92 (2) ◽  
pp. 647-667
Author(s):  
Wen-Hsiung Li
Keyword(s):  
Frequency Spectrum ◽  
Intermediate Frequency ◽  
Deleterious Mutations ◽  
Low Frequencies ◽  
Deleterious Alleles ◽  
Genic Variation ◽  
Controversial Problem ◽  
The Mean ◽  
Neutral Mutations ◽  
A Minor

ABSTRACT In order to assess the effect of deleterious mutations on various measures of genic variation, approximate formulas have been developed for the frequency spectrum, the mean number of alleles in a sample, and the mean homozy-gosity; in some particular cases, exact formulas have been obtained. The assumptions made are that two classes of mutations exist, neutral and deleterious, and that selection is strong enough to keep deleterious alleles in low frequencies, the mode of selection being either genic or recessive. The main findings are: (1) If the expected value () of the sum of the frequencies of deleterious alleles is about 10% or less, then the presence of deleterious alleles causes only a minor reduction in the mean number of neutral alleles ir, a sample, as compared to the case of = 0. Also, the low- and intermediate-frequency parts of the frequency spectrum of neutral alleles are little affected by the presence of deleterious alleles, though the high-frequency part may be changed drastically. (2) The contribution of deleterious mutations to the expected total number of alleles in a sample can be quite large even if is only 1 or 2%. (3) The mean homozygosity is roughly equal to (1-2)/(1+λ  1), where λ  1, is twice the number of new neutral mutations occurring in each generation in the total population. Thus, deleterious mutations increase the mean heterozygosity by about 2/ (1 +λ  1). The present results have been applied to study the controversial problem of how deleterious mutations may affect the testing of the neutral mutation hypothesis.

scholarly journals Genetic Basis of Transcriptome Diversity in Drosophila melanogaster

2015 ◽  
Author(s):  
Wen Huang ◽  
Mary Anna Carbone ◽  
Michael Magwire ◽  
Jason Peiffer ◽  
Richard Lyman ◽  
...  
Keyword(s):  
Gene Expression ◽  
Drosophila Melanogaster ◽  
Quantitative Trait ◽  
Genetic Basis ◽  
Trait Variation ◽  
Regulatory Variants ◽  
Genome Wide ◽  
Mean And Variance ◽  
The Mean

Understanding how DNA sequence variation is translated into variation for complex phenotypes has remained elusive, but is essential for predicting adaptive evolution, selecting agriculturally important animals and crops, and personalized medicine. Here, we quantified genome-wide variation in gene expression in the sequenced inbred lines of the Drosophila melanogaster Genetic Reference Panel (DGRP). We found that a substantial fraction of the Drosophila transcriptome is genetically variable and organized into modules of genetically correlated transcripts, which provide functional context for newly identified transcribed regions. We identified regulatory variants for the mean and variance of gene expression, the latter of which could often be explained by an epistatic model. Expression quantitative trait loci for the mean, but not the variance, of gene expression were concentrated near genes. This comprehensive characterization of population scale diversity of transcriptomes and its genetic basis in the DGRP is critically important for a systems understanding of quantitative trait variation.

scholarly journals SELECTION BY FERTILITY IN DROSOPHILA PSEUDOOBSCURA

Genetics ◽  
1974 ◽  
Vol 77 (3) ◽  
pp. 559-564
Author(s):  
Wyatt W Anderson ◽  
Takao K Watanabe
Keyword(s):  
Balancing Selection ◽  
Low Frequency ◽  
Chromosomal Polymorphism ◽  
Intermediate Frequency ◽  
Male Mating ◽  
Female Fecundity ◽  
Differential Fertility ◽  
High Frequencies ◽  
Differential Viability ◽  
Males And Females

ABSTRACT Fertility, the component of selection due to female fecundity and male mating success, differed significantly among the ST/ST, ST/AR, and AR/AR karyotypes in experimental populations and varied with karyotypic frequency. In relation to ST/AR, ST/ST females and males had higher fertilities at low frequency; AR/AR males and females were at a significant fertility disadvantage at intermediate frequency, while at low and at high frequencies their fertilities matched or exceeded that of the heterokaryotype. These fertility differences were comparable in size to viability differences previously reported for D. pseudoobscura karyotypes. Differential fertility seems likely to be an important element, perhaps just as important as differential viability, in the balancing selection that maintains the chromosomal polymorphism in this species.

scholarly journals Genetic basis of transcriptome diversity in Drosophila melanogaster

2015 ◽  
Vol 112 (44) ◽  
pp. E6010-E6019 ◽  
Author(s):  
Wen Huang ◽  
Mary Anna Carbone ◽  
Michael M. Magwire ◽  
Jason A. Peiffer ◽  
Richard F. Lyman ◽  
...  
Keyword(s):  
Gene Expression ◽  
Drosophila Melanogaster ◽  
Dna Sequence ◽  
Quantitative Trait ◽  
Genetic Basis ◽  
Protein Coding ◽  
Regulatory Variants ◽  
Genome Wide ◽  
Mean And Variance ◽  
The Mean

Understanding how DNA sequence variation is translated into variation for complex phenotypes has remained elusive but is essential for predicting adaptive evolution, for selecting agriculturally important animals and crops, and for personalized medicine. Gene expression may provide a link between variation in DNA sequence and organismal phenotypes, and its abundance can be measured efficiently and accurately. Here we quantified genome-wide variation in gene expression in the sequenced inbred lines of the Drosophila melanogaster Genetic Reference Panel (DGRP), increasing the annotated Drosophila transcriptome by 11%, including thousands of novel transcribed regions (NTRs). We found that 42% of the Drosophila transcriptome is genetically variable in males and females, including the NTRs, and is organized into modules of genetically correlated transcripts. We found that NTRs often were negatively correlated with the expression of protein-coding genes, which we exploited to annotate NTRs functionally. We identified regulatory variants for the mean and variance of gene expression, which have largely independent genetic control. Expression quantitative trait loci (eQTLs) for the mean, but not for the variance, of gene expression were concentrated near genes. Notably, the variance eQTLs often interacted epistatically with local variants in these genes to regulate gene expression. This comprehensive characterization of population-scale diversity of transcriptomes and its genetic basis in the DGRP is critically important for a systems understanding of quantitative trait variation.

scholarly journals Multilocus models of inbreeding depression with synergistic selection and partial self-fertilization

1991 ◽  
Vol 57 (2) ◽  
pp. 177-194 ◽  
Author(s):  
B. Charlesworth ◽  
M. T. Morgan ◽  
D. Charlesworth
Keyword(s):  
Inbreeding Depression ◽  
Mutation Rate ◽  
Approximate Expression ◽  
Heterozygote Advantage ◽  
Selfing Rate ◽  
Deleterious Alleles ◽  
Plausible Model ◽  
Computer Calculations ◽  
Mean Fitness ◽  
The Mean

SummaryMean fitness and inbreeding depression values in multi-locus models of the control of fitness were studied, using both a model of mutation to deleterious alleles, and a model of heterozygote advantage. Synergistic fitness interactions between loci were assumed, to find out if this more biologically plausible model altered the conclusions we obtained previously using a model of multiplicative interactions. Systems of unlinked loci were assumed. We used deterministic computer calculations, and approximations based on normal or Poisson theory. These approximations gave good agreement with the exact results for some regions of the parameter space. In the mutational model, we found that the effect of synergism was to lower the number of mutant alleles per individual, and thus to increase the mean fitness, compared with the multiplicative case. Inbreeding depression, however, was increased. Similar effects on mean fitness and inbreeding depression were found for the case of heterozygote advantage. For that model, the results were qualitatively similar to those previously obtained assuming multiplicativity. With the mutational load model, however, the mean fitness sometimes decreased, and the inbreeding depression increased, at high selfing rates, after declining as the selfing rate increased from zero. We also studied the behaviour of modifier alleles that changed the selfing rate, introduced into equilibrium populations. In general, the results were similar to those with the multiplicative model, but in some cases an ESS selfing rate, with selfing slightly below one, existed. Finally, we derive an approximate expression for the inbreeding depression in completely selfing populations. This depends only on the mutation rate and the dominance coefficient and can therefore be used to obtain estimates of the mutation rate to mildly deleterious alleles for plant species.

Whole-Genome Effects of Ethyl Methanesulfonate-Induced Mutation on Nine Quantitative Traits in Outbred Drosophila melanogaster

Genetics ◽  
2001 ◽  
Vol 157 (3) ◽  
pp. 1257-1265 ◽  
Author(s):  
Hsiao-Pei Yang ◽  
Ana Y Tanikawa ◽  
Wayne A Van Voorhies ◽  
Joana C Silva ◽  
Alexey S Kondrashov
Keyword(s):  
Drosophila Melanogaster ◽  
Quantitative Traits ◽  
Spontaneous Mutation ◽  
Developmental Time ◽  
Ethyl Methanesulfonate ◽  
Induced Mutations ◽  
Mean Values ◽  
Eye Color ◽  
Recessive Mutations ◽  
The Mean

Abstract We induced mutations in Drosophila melanogaster males by treating them with 21.2 mm ethyl methanesulfonate (EMS). Nine quantitative traits (developmental time, viability, fecundity, longevity, metabolic rate, motility, body weight, and abdominal and sternopleural bristle numbers) were measured in outbred heterozygous F3 (viability) or F2 (all other traits) offspring from the treated males. The mean values of the first four traits, which are all directly related to the life history, were substantially affected by EMS mutagenesis: the developmental time increased while viability, fecundity, and longevity declined. In contrast, the mean values of the other five traits were not significantly affected. Rates of recessive X-linked lethals and of recessive mutations at several loci affecting eye color imply that our EMS treatment was equivalent to ∼100 generations of spontaneous mutation. If so, our data imply that one generation of spontaneous mutation increases the developmental time by 0.09% at 20° and by 0.04% at 25°, and reduces viability under harsh conditions, fecundity, and longevity by 1.35, 0.21, and 0.08%, respectively. Comparison of flies with none, one, and two grandfathers (or greatgrandfathers, in the case of viability) treated with EMS did not reveal any significant epistasis among the induced mutations.

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